1. Field of the Invention
The present invention relates to a method and apparatus for processing an image in a color copying machine for normal paper recording and, more particularly, to a method and apparatus for processing an image wherein various parameters for image data formation can be automatically calculated.
2. Description of the Prior Art
In a conventional image processing apparatus such as a color copying machine using a laser beam, a laser beam must be modulated on the basis of final image data to form a latent image of a predetermined object on a photosensitive drum. In this case, image data for laser beam modulation must be generated on the basis of original image data.
In recent years, in order to record a halftone image, a laser beam tends to be modulated not by simple binary data but by image data of three or more values or analog image data.
It is important to balance image color densities particularly in a color copying machine.
A conventional image processing apparatus employs fixed threshold values for image data formation, thus posing the following problems.
(1) A so-called fog is formed in a recorded image when a document has a high background density level, thus degrading image quality.
(2) In order to eliminate a fog, it is effective to change the threshold values. However, it is very difficult to manually change the threshold values without skills.
(3) When output characteristics of a document reading apparatus are changed by external factors, a good color balance cannot be maintained. The only way of recovering a good color balance is to set the threshold values again by observing the recorded image. Therefore, more advanced skills are required.
Conditions in units of colors at the time of image data generation are not limited to the threshold values but must also include an MTF correction parameter.